1. Field of the Invention
The present invention relates to an antenna device and a wireless communication device using the antenna device, and particularly to the structure of a dual-band antenna.
2. Description of Related Art
Smartphones and other portable wireless terminals have a basic communication function that is used for connection to a communication line, and various other communication functions, such as GPS, Wi-Fi, Bluetooth, and NFC. In order to efficiently put those communication functions in a limited space, the use of a dual-band antenna is effective. It is known that, if two feeding points of the dual-band antenna are disposed close to each other, mutual interference occurs, leading to a deterioration of antenna characteristics. Therefore, in the case of the dual-band antenna, it is necessary to prevent the deterioration of antenna characteristics associated with the mutual interference. For example, in the antennas disclosed in Japanese Patent Application Laid-Open No. 2008-252506 and Japanese Patent No. 4,973,700, a secondary resonance mode is used to solve the above problem.
However, the problem is that a conventional antenna that makes use of a secondary resonance mode is larger in size than an antenna that only uses a primary resonance mode. It is possible to reduce the size of the antenna by adopting a folded pattern for a radiation pattern formed on a surface of a dielectric block to secure the length of the pattern. However, such a configuration leads to a deterioration of antenna radiation characteristics. Therefore, it is hoped that an improvement will be made by other methods.